Safety mechanism for railway switch machines



A ril 4, 1967 R. w. KUGLER ETAL 3,312,819

SAFETY MECHANISM FOR RAILWAY SWITCH MACHINES 2 Sheets-Sheet 1 Filed April 30, 1964 April 4, 1967 R. w. KUGLER ETAL SAFETY MECHANISM FOR RAILWAY SWITCH MACHINES Filed April 50, 1964 2 Sheets-Sheet 2 d f W W i W. Wmwm 6 United States Patent Ofitlce 3,312,819 SAFETY MECHANISM FOR RAILWAY SWITCH MACHLNES Ralph W. Kugler, Brookline, and Robert A. Wenston, Pittsburgh, Pa., assignors to Westinghouse Air Brake Company, Swissvale, Pa.

Filed Apr. 30, 1964, Ser. No. 363,751

17 Claims. (Cl. 246--221) Our invention relates to electrically operated railway switch machines, and more particularly to an improved safety mechanism which provides positive interruption of the supply of power to said switch machine whereby the switch machine may at times be manually operated without danger or risk.

In many instances, such as, for example, during times of inspection, maintenance or emergency operation, it becomes necessary to manually manipulate a switch machine between its normal and reverse positions. Normally, this manual operation for moving the switch between its two extreme positions is accomplished by means of a hand crank which may be suitably positioned within the switch machine. It has been found, however, that prior to permitting any manual operation of the switch machine it is desirable to reliably insure that the supply of electrical power, particularly to the electric motor of the switch machine, is interrupted. This positive interruption of electrical power to the switch motor precludes the automatic or remote actuation of the switch machine and allows an operator to safely manually operate the switch machine.

Further, once placed in its manually operated position, it is desirable, from the standpoint of safety, to lock the switch machine in this position. Such an arrangement provides an unlock-to-release feature which insures that an unauthorized person is unable to return the switch machine to its automatic electrical condition of operation and only permits authorized pe1sonnel familiar with the situation at hand to restore the switch machine to the automatic electrical condition of operation.

It is also desirable, from the standpoint of safety, to positively interrelate the circuit cutout contacts and the crank access means so that the chance of manually operating the switch machine while the contacts still complete the power circuit is substantially eliminated. In prior art switch machines the circuit interrupter or switch, which completed the power circuit, was coupled to the crank guard, which prevented the insertion of the crank into the switch machines, through linkage which was susceptible to mechanical failure. In case of linkage failure an operator could still operate the switch machine by hand unknowing that the power was still on, which is clearly a dangerous and undesirable condition.

It is therefore an object of our invention to provide an electric switch machine with an improved protective device which permits safe manual operation of said machine during times of inspection, maintenance or emergency operation.

A further object of our invention is to provide an improved slidable safety mechanism for switch machines which is of simple and economical construction.

A further object of our invention is to provide an improved safety device which positively interrupts the supply of power to electric switch machines and which permits manual operation of said switch machines without danger or risk.

A still further object of our invention is to provide an electrical switch machine with an improved safety selector which may be freely moved by an operator to condition said switch machine for manual operation but which is normally prevented from restoring said switch machine 3,312,819 Fatented Apr. 4, 1967 to an automatic condition of operationby means of a key-type lock.

Another object of our invention is to provide an improved safety device having unitarily constructed means for carrying the supply circuit cutout contacts and the hand crank access means whereby positive interruption of the supply of power to the switch machine is insured prior to permitting the manual manipulation of said switch machine.

Further objects, features, and advantages of our invention will become more apparent as the following description proceeds and the features and novelty which characterize our invention will be pointed out with particularity in the claims appended which form part of our specification.

Briefly stated, our invention relates to a safety apparatus for selectively conditioning an electrical switch machine between a manual condition of operation and an automatic condition of operation for moving a railway switch between its normal and reverse positions. The safety apparatus is conveniently mounted and housed within the motor compartment of said switch machine. A hinged cover normally closed during electrical operation of said switch machine provides immediate access for selectively changing the operational condition of said switch machine. An L-shaped base member is suitably secured to a sidewall of the motor compartment and includes a guideway for slidably supporting an integral bracket which is adapted to be moved between a first and a second extreme position. The movable bracket includes an integrally formed hand'lever pin, guard plate and contact plate. The hand-lever pin has an outer portion which is readily accessible to an operator for moving the bracket between its first and second extreme position. The guard plate includes a crank access aperture which is normally out of alignment with a crank socket and ordinarily prevents an opeartor from inserting a hand crank to manually manipulate the switch machine. The contact plate includes switch elements which normally make contact with U-shaped spring contacts mounted on said base member for completing appropriate power circuits to the switch machine. A forked member suitably couples the inner portion of said hand-lever pin with a cylindrical-type lock assembly also suitably secured in spaced relation to the sidewall of said motor compartment. The cylindrical-type lock assembly operates to positively lock the movable bracket in its second position. Further, a stop member mounted on the hinged cover cooperates with the outer portion of said hand-lever pinto prevent closing of the hinged cover during times when the bracket is in its second position.

During electrical operation of the switch machine the integral bracket is in its first extremeposition so that the crank access aperture is out of alignment with the crank socket, thereby preventing insertion of the hand crank, and the switch elements make contact with the shaped spring contacts so that the electrical circuits to the switch machine are completed. However, during manual condition of operation of said switch machine the integral bracket is shifted to the second extreme position so that the crank access aperture is placed in alignment with the crank socket and insertion of the crank is permitted and the switch elements break contact with the U-shaped spring contact so that electrical energization of the switch machine is prevented. As mentioned above, the safety mechanism is locked in this position by the cylindrical-type lock assembly and the hinged cover is prevented from being closed by means of the stop member cooperating with the outer portion of the hand-lever pin, thereby indicating that the machine is under manual operation.

A better understanding of our present invention will be had by reference to the drawings, in which similar characters of reference refer to similar parts throughout the several views, and in which:

FIG. 1 is a partial top plan view of an electrical switch machine with portions broken away for better illustrating the novel safety mechanism embodying the present invention.

FIG. 2 is a partial side elevation of the embodiment shown in FIG. 1.

FIG. 3 is an enlarged view of the safety mechanism taken substantially along the line III-III of FIG. 2.

FIG. 4 is an enlarged fragmentary top plan view partially in section of the safety mechanism shown in FIG. 1.

FIG. 5 is an isometric view of the contact bracket assembly utilized in the presently disclosed embodiment with the respective circuits to the switch machine being interrupted by the switch elements.

FIG. 6 is a fragmentary sectional view of a lock assembly in its locked position with a proper key inserted therein and taken along lines VI-VI of FIG. 3.

Referring to FIGS. 1 and 2 of the drawings, our invention is shown in application with an electric railway switch machine 10 which may be suitably mounted in the usual manner adjacent a railway track switch S shown diagrammatically in FIG. 1. The switch machine 10 includes a housing or casing 11 which is formed with a motor compartment 12. The motor compartment 12 is closed at its upper end by the removable cover 13 and is closed at one side by a hinged hand-crank cover 14 which may be suitably padlocked by means of a conventional staple and hasp arrangement.

The safety device, generally illustrated by character 15, is shown mounted within motor compartment 12 and is suitably secured to the side wall of housing 11 by means of bolts 17 (see FIGS. 3 and 4). A shaft 18 for manually operating the switch machine is shown mounted above the safety device, as viewed in FIG. 1. The right-hand end of shaft 18, as viewed in FIGS. 1 and 2, is connected by means of universal joint 12 to a reduction gear shaft 20 which may be appropriately connected by any well-known mechanical advantage gear train GT, shown diagrammatically in FIG. 1, for operating the switch between its normal and reverse positions. The left-hand end of shaft 18 is provided with a suitable crank socket 21 and is journaled in a self-aligning ball hearing held by bearing bracket 22 which, in turn, is suitably secured by bolts 23 on the side wall of housing 11. A hearing support 24 including a bearing for accommodating the hand crank is aligned with the crank socket 211. Bearing support 24 is suitably secured to the outer side of the side wall of housing 11 by bolts 16.

Referring now to FIGS. 3 and 4, these figures show in greater detail the safety device or selector of our present invention. In FIGS. 3 and 4, the selector 15 is illustrated in its normal or automatic condition of operation, that is, the contacts complete the circuit to the power supply and the crank access means prevents insertion of a hand crank for manual operation. Substantially, all the parts of the safety device 15 are supported on an Lshaped base member 25 which, as previously pointed out, is securely fastened to the side wall of the housing 11 by bolts 17. A pair of insulating blocks 26 and 27 are secured to the top side of the horizontal leg portion of the L-shaped base member 25. A pair of spaced terminal posts 28 and 29 securely fasten a pair of U-shaped spring contacts 30 and 321, respectively, to the terminal block 26. Similarly, a pair of terminal posts 32 and 33 securely fasten a pair of U-shaped spring contacts 34 and 35, respectively, to terminal block 27. Terminal posts 28 and 29 are appropriately connected by conductors 36 and 37, partially shown in FIGS. 3 and 4, to the indication circuit of the switch machine while terminal posts 32. and 33 are appropriately con- 4 nected by conductors 33 and 39 into the circuit for the operating motor M of the switch machine shown diagrammatically in FIG. 4.

A pair of guide members 39 and 40, suitably spaced relative to each other, are securely fastened to the vertically extending leg portion of the L-shaped base member 25. The guide members 39 and 40 provide a suitable guideway for appropriately accommodating the guard plate 41 of a movable bracket 42, which is shown in perspective in FIG. 5. The movable bracket 42 is an integrally fabricated structure consisting of a vertically disposed guard plate 41, a horizontally extending contact plate 43, and a horizontally extending hand-lever pin or handle 44. The guard plate 41 of bracket 42 cooperates with the guideway formed by guide members 39 and 40 so that the complete bracket 42 is vertically slidable between an upper manual position and a lower automatic position, which will be more fully described hereinafter.

Two insulating blocks 45 and 4:? are secured by tap screws 47 and 48, respectively, on opposite faces of contact plate 43 at the end remote from guard plate 41. A pair of heavy duty U-shaped switch elements or contactors 49 and 50 are disposed adjacent insulating blocks 45 and 46, respectively, and insulated from contact plate 43 by the insulative securing arrangement 51, as shown in detail in FIG. 4. The insulative securing arrangement 51 includes an insulating tubing 52 which passes through suitable aligned openings provided in plate 43, insulating blocks 45 and 46, and switch elements or contacts 49 and 59. Insulating spacers or washers 53 are positioned at the opposite ends of tubing 52, and a screw 54 passes through the insulating spacers or washers and through the tubing 52. 'The screw 54 also passes through metal washers 55 on the outer faces of the insulating washers. A nut 56 is inserted on the end of the screw to hold all of the foregoing parts in assembled relation.

A lock assembly unit, generally illustrated at 57, is also secured to the vertically extending leg portion of the L-shaped base member 25. The lock is of the cylinder type and includes a cylindrical plug 58 which passes through suitable apertures formed in the vertical leg portion of base member 25 and lock casing 59. Referring now to FIG. 6 of the drawing it is noted that the lock unit is illustrated, as a matter of convenience, in its locked position with a key ea inserted in position. This manual position of the lock unit is shown for the purpose of more clearly illustrating the key retaining feature of the lock unit. When the lock unit is in this manual or locked position, the key 6 cannot be removed since the retainer pin 61 coacts with a slot 66a in the key and prevents lateral movement, that is, withdrawal of the key. A spring 62 constantly urges retainer pin 61 upwardly and is retained in its position by an adjustable screw 63. The pins 64, slugs 65, biasing springs 66 and tumbler screws 67 operate in a conventional manner to normally lock the lock unit in this manual position and only permit rotation of the lock cylinder plug 58 after the insertion of the proper key, as illustrated in FIG. 6. The inner end of cylinder plug 58 is provided with a threaded portion 68 which carries a spring washer 69, a lock operating fork 7t), metallic washer 71 and a stop nut 72 which holds these elements in proper cooperative relation with one another. A look housing 73 partially surrounds the lock unit 57 and is provided with apertures 74 for providing access so that tumbler screws 67 may be adjusted. The bifurcated end of lock operating fork is disposed in cooperative relationship with the inner end of hand-lever pin 44. As is readily apparent, the lock operating fork 76 transmits the vertical motion of the movable bracket 42 to the lock cylinder 53 whereby the cylinder plug 53 is rotated between its locked and unlocked positions.

Under normal operating conditions, the safety device or selector is in its lower automatic position of operation,

as clearly illustrated in FIG. 3, and the switch machine is driven between its normal and reverse positions in the conventional manner by the motor M shown diagramatically in FIG. 4. In this automatic position of operation, the switch elements or c-ontactors 49 and 50 complete the cincuits to the motor and indication means of the switch machine and the aperture 75 in guard plate 41 remains out of alignment with the crank socket so that an operator is prevented from inserting a hand crank into socket 18.

Now assuming that an operator desires to manually manipulate the switch machine, such as may exist during periods of maintenance, inspection or emergency operation, initially, the operator opens the hand crank cover 14 which permits access to the hand-lever pin 44. The operator now lifts the hand-lever pin 44 which results in interrupting the circuits to the indication means and to the motor by disconnecting the bridging efiect of switch elements 49 and 50 from the contacts 30, 31 and 34, 35, respectively. The upward movement of lever pin 44 also brings aperture 75 in alignment with the crank socket 18 so that the hand crank may be freely inserted into the socket by the operator. The upward movement of the hand-lever pin 44 also causes cylinder 58 of the lock unit to rotate through lock operating fork 7t and upon reaching the upper or manual position the tumblers act to lock the entiremechanism in this position until a proper key is subsequently inserted into the lock unit. This unlock-to-release feature prevents unauthorized personnel from returning the switch machine to its automatic position of operation and only permits responsible personnel familiar with the situation to return the switch machine to its automatic condition of operation. Further, a cover stop 7-6 interacts with the outer end of the hand-lever pin 44 for preventing the hand crank cover 14 from being closed when the safety device is in the manual position of operation. This cover stop insures that an operator may not inadvertentlyclose the hand-crank cover and leave the safety device in its manual condition of operation. Further, this prevents subsequent trainmen from being locked out and manually operating the switch machine and acts as a reminder to the maintainer that the switch machine is in manual condition of operation.

, Now prior to returning the machine to its automatic position, a maintainer must insert a proper key which acts to unlock the lock unit as shown in FIG. 6. The maintainer now withdraws the hand crank, if he has not previously done so, and moves the hand-lever pin 44 downward-1y wherein the switch elements or contactors 49 and 50 close the circuit through contacts 30, 3d, and 34, 35, respectively, to theindication means and motor circuits. The operator may now withdraw the key from the lock unit since the slot 60a no longer engages the retaining pin 61 due to the relative angular rotation of the lock cylinder caused by the downward movement of the hand lever. Further, the operator may now close the hand-crank cover 14 and, if so desired, padlock through the staple-hasp arrangement.

It is readily noted the present invention provides that the switch machine be readily moved to its manual position of operation but insures that only authorized personnel, such as, for example, a maintainer, can return .the switch machine to its automatic position of operation. Further, the simple integral structure of the safety mechanism insures at all times that the contacts interrupt the power supply prior to permitting any manual operation of the switch machine. This results in the utmost of safety to personnel as well as to equipment.

While our invention has been described with reference to a single embodiment thereof it should be understood that numerous other embodiments may be devised by those skilled in the art that will fall Within the spirit and scope of our invention. Our invention, therefore,

is not restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

Having thus described our invention, what we claim is:

1. A safety device for selectively controlling the opera tional state of an electrical machine comprising, a unitized bracket means movable between two extreme positions and including handle means for manually moving said unitized bracket means between said two extreme positions, contact means for establishing an electrical circuit for the electrical machine when said unitized bracket means is in a first one of said two extreme positions and for interrupting the electrical circuit when said unitized bracket means is in the second of said two extreme positions, and guard means for preventing manual operation of the electrical machine when said bracket is in said first extreme position.

2. A safety device as defined operated lock means locks said unitized bracket means in said second extreme position thereby preventing said unitized bracket means from being returned to said first extreme position until a proper key is inserted in said key operated lock means.

3. A safety device as defined in claim 1 wherein, said unitized bracket means is cooperatively associated with a guideway which slidably guides said unitized bracket means between said two extreme positions.

4. A safety device as defined in claim 1 wherein, the electrical machine includes a housing for enclosing said device and a cover for providing ready access to said handle means.

5. A safety device as defined in claim 4 wherein, said cover includes a stop member which cooperates with said handle means for preventing closure of said cover when said unitized bracket means is in said second extreme position.

6. A safety mechanism for selectively determining the operational condition of an electrical switch machine comprising, a unitized assembly means slidable between a first and a second position, means for manually moving said assembly means between said first and second positions, means completing an electrical circuit to said switch machine for permitting electrical operation of said switch machine when said assembly means is in said first position, means for preventing manual operation of said switch machine when said assembly means is in said first position, andmeans for locking said assembly means in said second position and permitting the return of said assembly means to said first position only after insertion of a proper key into said locking means.

7. A protection mechanism for selectively conditioning an electrical switch machine between a manual condition of operation and an automatic condition of operation comprising; a slidable bracket means including a unitarily constructed hand-lever means, guard means and contact means; said hand-lever means being readily available for in claim 1 wherein, a key manual manipulation, said guard means having an aper ture which permits the insertion of a hand crank during said manual condition of operation, said contact means having electrical contacts for positively interrupting the supply of power to said switch machine during said manual condition of operation, and locking means cooperatively associated with said bracket means for locking said mechanism in said manual condition of operation.

8. In an electrical railway switch machine normally electrically operated between normal and reverse positions, a safety device for permitting said switch machine to be manually operated between said normal and reverse positions; said safety device including a bracket assembly having an integrally formed handle, guard plate and contact means; said handle adapted to move said bracket assembly between a first and a second position, said guard plate normally preventing manual operation of said switch machine when said bracket assembly is in said first position and permitting manual operation of said switch machine when said bracket assembly is in said second prising, a casing,

position, and said contact means permitting electrical operation of said switch machine when said bracket assembly is in said first position but preventing electrical operation of said switch machine when said bracket assembly is in said second position.

9. A safety device for selectively establishing the operational state of an electrical switch machine comprising, a bracket assembly slidable between two extreme positions, hand-lever means for moving said bracket assembly between said two extreme positions, contact means completing an electrical circuit to said switch machine for permitting electrical operation of said switch machine when said bracket assembly is in a first one of said two extreme positions, guard means for preventing manual operation of said switch machine when said bracket assembly is in said first extreme position, and key operated means for locking said bracket assembly in the second of said two extreme positions whenever said bracket assembly is moved to said second extreme position.

19. A protective device for selectively conditioning an electrical switch machine between an automatic condition of operation and a manual condition of operation comprising; a movable bracket assembly including an integrally formed handle, guard plate and contact plate; said handle being adapted to move said bracket assembly between said automatic and manual condition of operation, said guard plate having an aperture which exposes a handcrank socket during the manual condition of operation, said contact plate having electrical contacts for interrupting the supply of power to said switch machine during the manual condition of operation, and a lock assembly cooperatively interconnected with said bracket means for locking said device in its manual condition of operation.

11. In an electrical railway switch machine normally electrically operated between normal and reverse positions but at times manually operable between said normal and reverse positions, a safety mechanism for preventing said switch machine from being manually operated between said normal and reverse positions except when the electrical operating means is deenergized; said safety mechanism including a bracket assembly having an integrally formed handle, guard plate and contact means; said handle adapted to move said bracket assembly between a first and a second position, said guard plate normally preventing manual operation when said bracket assembly is in said first position and permitting manual operation when said bracket assembly is in said second position, said contact means permitting electrical operation when said bracket assembly is in said first position but preventing electrical operation when said bracket assembly is in said second position, and locking means cooperatively connected to said bracket assembly for locking said mechanism in said second position.

12. A safety mechanism for selectively determining the operational condition of an electrical switch machine coma cover, a unitized bracket assembly mounted within said casing and slidable between two extreme positions, a hand-lever pin for moving said bracket assembly between said two extreme positions, a circuit contact for completing an electrical circuit to said switch machine for permitting electrical operation of said switch machine when said bracket assembly is in a first of said two extreme positions, a guard plate for preventing manual operation of said switch machine when said assembly means is in said first extreme position, a lock assembly for locking said bracket assembly in the second of said two extreme positions and permitting the return of said assembly means to said first position only after insertion of a proper key into said locking means, and a cover stop cooperating with said hand-lever pin to prevent closing of said cover until said bracket assembly is returned to said first position.

13. A safety mechanism for selectively conditioning an electrical switch machine for a manual condition of operation or an automatic condition of operation comprising, a casing, a cover; a slidable bracket mounted within said casing and including an integrally formed handle, guard plate and contact plate, said handle being readily accessible to an operator for manual manipulation, said guard plate having an aperture which permits the insertion of a hand crank during the manual condition of operation, said contact plate having electrical contacts which interrupt the supply of power to said switch machine during the manual condition of operation, a lock assembly cooperatively associated with said bracket means for locking said mechanism in its manual condition of operation, and a cover stop on said cover cooperating with said handle to prevent said cover from being closed until said mechanism is returned to the automatic condition of operation.

14. In an electrical railway switch machine normally electrically operated between normal and reverse positions, a housing, a hinged cover located on one side of said housing, a safety device for permitting said switch machine to be manually operated between said normal and reverse positions; said safety device mounted within said housing and including a bracket assembly having an integrally formed handle, guard plate and contact means; said handle adapted to move said bracket assembly between a first position and a second position, said guard plate normally preventing manual operation when said bracket assembly is in said first position and permitting manual operation when said bracket assembly is in said second position, said contact means permitting electrical operation when said bracket assembly is in said first position but preventing electrical operation when said bracket assembly is in said second position, locking means cooperatively related to said bracket assembly for locking said device in said second position, and a stop means located on said cover and cooperating with said handle to prevent closure of said cover when said switch machine is in its manual condition of operation.

15. A safety mechanism for electrical railway switch machines comprising, a base member secured to said switch machine and having first and second leg portions, a guideway disposed on said first leg portion of said base member, a movable bracket cooperating with said guideway and slidable between a first and a second position for selectively controlling the electrical condition of said switch machine; said movable bracket including an integrally formed hand-lever pin, guard plate and contact plate; said hand-lever pin readily accessible to an operator for moving said bracket between said first and second ositions, said guard plate having a crank acces aperture which is out of alignment with a crank socket when said movable bracket is in said first position and which is in alignment with said crank socket when said movable bracket is in said second position, said contact plate having switch elements which make contact with electrical contacts mounted on said base member when said movable bracket is in said first position and which break contact with said contacts when said movable bracket is in said second position, and a key-type lock assembly coupled to said movable brac tet and effective to lock said bracket in said second position.

16. A safety mechanism for electrical railway switch machines comprising, an L-shaped base member secured to said switch machine and having vertical and horizontal leg portions, a guideway disposed on said vertical leg portion of said base member, a movable bracket cooperating with said guideway and slidable between a first and a second position for selectively controlling the electrical condition of said switch machine; said movable bracket including an integrally formed hand-lever pin, guard plate and contact plate; said hand-lever pin having an outer portion readily accessible to an operator for manually moving said bracket between said first and second positions, said guard plate having a crank access aperture which is out of alignment with a crank socket when said movable bracket is in said first position and which is in alignment with said crank socket when said movable bracket is in said second position, said contact plate having switch elements which make contact with U-shaped electrical contacts when said movable bracket is in said first position for providing electrical power to said switch machine and which break contact with said contacts when said movable bracket is in said second position for interrupting the electrical power to said switch machine, and a key-type lock assembly coupled to said movable bracket and adapted to lock said bracket in said second position thereby permitting safe manual operation of said switch machine.

17. In an electrical railway switch machine having a housing, a hinged cover secured to said switch machine, and a safety mechanism comprising, an L-shaped base member secured to said switch machine and having vertical and horizontal leg portions, a guideway disposed on said vertical leg portion of said base member, a movable bracket cooperating with said guideway and slidable between a first and a second position for selectively conthe electrical condition of said switch machine; said movable bracket including an integrally formed handlever pin, guard plate and contact plate; said hand-lever pin having an outer portion readily accessible to an operator for moving said bracket between said first and secsaid guard plate having a crank access aperout of alignment with a said movable bracket is in said first position and which is in alignment with said crank socket when said movab? bracket is in said second position, said contact plate having switch elements which make contact with U-shaped spring contacts mounted on said base member when said movable bracket is in said first position and which break contact with said U-shaped spring contacts when said movable bracket is in said second position, a stop member disposed on said hinged cover and cooperating with said outer portion of said hand-lever pin to prevent said cover from being closed when said bracket is in said sec ond position, and a cylindrical type lock assembly secured to said switch machine and coupled to said movable bracket and adapted to lock said bracket in said second position.

References Cited by the Examiner UNITED STATES PATENTS 1,716,787 6/1929 McWhirter 246-393 X 1,785,698 12/1930 Howe 246-393 X 1,886,955 11/1932 Howe 246242 2,045,930 6/1936 Taylor 246-393 2,092,828 9/1937 Bone 246-393 X 2,707,230 4/1955 Beltman et al 246393 X 2,986,630 5/1961 Maynard 246-221 X ARTHUR L. LA POINT, Primary Examiner. S. B. GREEN, Assistant Examiner. 

1. A SAFETY DEVICE FOR SELECTIVELY CONTROLLING THE OPERATIONAL STATE OF AN ELECTRICAL MACHINE COMPRISING, A UNITIZED BRACKET MEANS MOVABLE BETWEEN TWO EXTREME POSITIONS AND INCLUDING HANDLE MEANS FOR MANUALLY MOVING SAID UNITIZED BRACKET MEANS BETWEEN SAID TWO EXTREME POSITIONS, CONTACT MEANS FOR ESTABLISHING AN ELECTRICAL CIRCUIT FOR THE ELECTRICAL MACHINE WHEN SAID UNITIZED BRACKET MEANS IS IN A FIRST ONE OF SAID TWO EXTREME POSITIONS AND FOR INTERRUPTING THE ELECTRICAL CIRCUIT WHEN SAID UNITIZED BRACKET MEANS IS IN THE SECOND OF SAID TWO EXTREME POSITIONS, AND GUARD MEANS FOR PREVENTING MANUAL OPERATION OF THE ELECTRICAL MACHINE WHEN SAID BRACKET IS IN SAID FIRST EXTREME POSITION. 